Sonic Visualizer

Downloaded the free sonic visualizer, and uploaded the car_pb.wav sound file into it.  A little bit of playing with the values and using the playback feature to listen and pause the sound when I hear the noise that I want.  OK, a lot of high frequency stuff – not what I’m looking for – I want something that cycles below the 60 Hz level, slower than a computer fan sound.  Also, I want a dominant frequency at some times since I can hear it above the background noise.  So, looking at the spectrum, I pick up 2 strong bands, one at 27 and one at 22 Hz.  Still too fast, though, I need something in the 0.1 Hz region, that is cycling once every 10 seconds.  x axis is time, y axis is frequency on a log scale.  Need to figure out how to zoom in.  Had it working, but went too low.  Will try again after I give the dogs a flea-tick bath.

Engine idle is just under 1000 rpm (or 1000/60=16.7 Hz).  Here is another picture with the low frequency oscillation viewed in the idle frequency (about 15-16 Hz see arrow).

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